This is an English translation of a news release in Japanese on August 16.

The Skin Care Laboratory, Material Science Laboratory, and Analytical Science Laboratory of Kao Corporation (President, Michitaka Sawada) have jointly developed a novel formulation based on effective combination of "large water-content α-gel"*1 with a unique polymer that is selectively absorbed in skin micro-scaling*2 regions (Fig. 1). Application of this formulation, developed during the course of our study targeting individuals who suffer from skin roughness caused by dry skin, has been shown to cause prompt improvement in smoothness of the corneocyte layer.

The research results will be presented at the 58th Annual Meeting of the Japan Oil Chemists' Society (September 24-26, 2019, Tokyo) and Okinawa Colloids 2019 (November 3-8, Okinawa Prefecture).

*1 Large water-content α-gel: Lamellar structure holding large amount of water between lipids.

*2 Micro-scaling: A condition in which the horny layer skin is thinly exfoliated in pieces.

Background

A large number of Japanese women suffer from dry skin, with the ratio recently shown to be increasing*3 . According to a survey conducted by Kao Corporation of actual skin state and awareness of working women with dry skin problems, more than 90% were found to have micro-scaling (Fig. 2) on the skin surface*4 .
On the surface of healthy smooth skin, corneocytes show moderate adherence to each other and form a well-ordered structure.. However, when skin is rough or damaged, micro-scaling appears where corneocytes exfoliate, thus it is considered that water evaporation has been accelerated, making the skin susceptible to outside stimuli.
Kao Corporation has developed "large water-content α-gel", which features a structure that is modeled on that of intercellular lipids of the corneocyte and provides a high water-holding capacity, for moisturizing areas of dry skin roughness and with wide application in a variety of skin care products. In the present trial, taking into consideration survey findings showing that working women want to experience skincare effects within a shorter period of time, possibly 3 to 7 days*5 , Kao researchers tested their technology developed for conditioning skin to provide smoothness within a short time period.

New technology for rapid smoothness of corneocyte surface

Kao researchers examined an approach to provide physical re-adhesion of corneocytes on the outermost skin surface that is soon to reach an exfoliated condition. Attention was focused on polymers and their multipoint adhesion characteristics. Following an intensive screening process, a unique polymer termed OXP-SI (oxazoline-modified silicone) was shown to form a flexible membrane as well as a capability to be combined with "large water-content α-gel". From repeated experiments that examined various methods, Kao researchers succeeded in development of a new formulation technology.
For confirming the characteristics of the formula, fluorescent microscopy examinations of OXP-SI polymer modified with fluorochrome were performed (Fig. 3). With conventional formulations, polymers are dispersed in an aqueous condition. In contrast, with the new formulation, it was confirmed that the polymer formed a unique complex surrounding the "large water-content α-gel" and then were dispersed in the aqueous phase.

Next, additional fluorescent microscopy examinations were performed following application of the new formula to human skin. The findings confirmed that applied "large water-content α-gel" combined with OXP-SI polymer was selectively absorbed in regions with micro-scaling (Fig. 1).
For further testing, 7 male and female subjects were asked to participate in examinations of an experimentally prepared skin roughness model*6 produced on the inner side of the forearm. The new formulation was applied to the model area twice a day and the skin surface was observed. Those results indicated that the model rough skin areas showed significant improvement from the second day of application with the new formulation as compared to the skin condition prior to application (Fig. 4).

*6 A solvent was topically applied to areas of skin to intentionally cause roughness.

Based on these findings, it was concluded that rough skin surfaces had smoothness repaired early, as the absorbed complex functioned to re-adhere regions with scaling to maintain a pseudo-healthy skin state.

Conclusion

Kao researchers successfully developed a novel technique for combining "large water-content α-gel" with a unique OXP-SI polymer in a liquid solution. This novel formulation was found to improve the skin surface condition soon after beginning applications, as selectively adherence was shown in areas of micro-scaling. It is considered that a smooth skin surface improves not only skin dryness but also provides an excellent condition for makeup finish. Findings obtained in this study will be used for future development of advanced skincare technology.